1. Field of the Disclosure
This disclosure relates to aqueous dispersions, and in particular to fixer inks for use with ink jet inks and methods of printing substrates.
2. Description of Related Art
Ink jet printing is a non-impact printing process in which droplets of ink are deposited on a substrate, such as paper or textile, to form the desired image. The droplets are ejected from a printhead in response to electrical signals generated by a microprocessor.
Most inkjet printers are equipped with an ink set comprising two or more different inks and are able to print black text and multicolor images. Typically, an ink set will comprise at least a cyan, magenta and yellow colored ink and a black ink (CMYK ink set).
For printing text, it is desirable for the black ink to have high optical density. For this purpose, a pigment colorant is most advantageous, especially a carbon black pigment. A pigment colorant is not soluble in the ink vehicle and must be treated in order to cause it to remain dispersed and jet properly. To effect dispersion stability, pigments are commonly treated with dispersants, and a wide variety of such materials have been disclosed. Especially effective are block copolymer dispersants which are described, for example, in U.S. Pat. Nos. 5,085,698, 5,519,085, 5,272,201, and 5,648,405. Amphoteric (sometimes referred to as polyampholyte) dispersants, i.e., dispersants containing moieties capable of reacting with acidic and basic reagents, for improved dispersion stability, have also been described. For example, U.S. Pat. No. 5,648,405 discloses an amphoteric dispersant formed of MAA/DMAEMA/BZMA random copolymer.
Typically substrates onto which images are printed are porous, eg. Paper or textile, and the printed image has a tendency to be absorbed into the substrate resulting in an image that has lower optical density. It is desirable for the image to sit on the surface of the substrate to improves its optical density, but it is also a requirement that this image be held in place to minimize or eliminate ink smear.
Despite the successful inkjet inks and print methods presently available, there is still a need for ink jet printed images having good optical density in combination with improved smear resistance.